Changing the grayscale range within a height map

[waldronate]

Wilbur can do this, but it's a little convoluted to get your mapping. The first step is to set a shader that will map altitude directly to color (done as a code block to make the indentation stay):

Do Texture>>Shader Setup  to bring up the Lighting Settings property page
    Select the General Tab
        Select Display Type as Height Code.
    Select Altitude Tab
        Turn on Absolute Coloring
        Set Altitude Max to 255
        Set Altitude Min to 0
        Click Color List on the Land side to bring up the Edit Color List dialog
            Hold down Shift and click Remove to clear the color list
            Click Add... and select Black (RGB 0,0,0)
            Click Add... and select White (RGB 255,255,255)
            Click OK to accept the Edit Color List changes
        Click OK to accept the Lighting Settings changes. Your surface should appear as grayscale with 0 as black and 255 as white.

If you need to remap your surface to a particular range of values (let’s say that another image editor has adjusted your data to the range 0 to 255 and you want it to the range 50 to 155), then use Filter>>Mathematical>>Span and enter your desired high and low values (50 and 155 in this case). After clicking OK, your surface will be displayed as you wanted.
Save the texture using File>>Save As and set File Type as BMP Texture or PNG Texture. It’s the texture that you want here, not the surface.